1. FIELD OF THE INVENTION
The present invention relates to computer graphics processing, and, more particularly, to an image processing apparatus and method capable of carrying out a blur process for giving a blur effect to an afterimage or the like of an object which is out of focus or moving fast.
2. DESCRIPTION OF THE RELATED ART
A computer graphics processing technique is used in a simulation apparatus, a game machine and the like. Normally, a simulation or game is implemented by a computer program, each object of an image is moved or the position of an observing point, the angle of visibility or the like is altered in accordance with the manipulation by an operator, and the image is then displayed on a display unit such as a monitor TV.
In this case, for example, position coordinates on the display screen are acquired by perspective transformation from three-dimensional coordinates to two-dimensional coordinates based on the position information of each object which is acquired by performing an arithmetic operation according to a computer program, and image data including pixel-by-pixel color information is obtained by a rendering process (filling process) based on information of the position coordinates and texture data, such as the display colors and patterns of individual objects, and is written in a frame buffer memory. The pixel-by-pixel color data written in the frame buffer memory is displayed on a monitor TV or the like after being subjected to D/A conversion.
As discussed above, main image processing includes a transformation process for the positions of a plurality of polygons which constitute an object and a rendering process for performing color filling on the polygon through both of which pixel-by-pixel image data is acquired and stored in the frame buffer memory. Each of those processes itself requires a lot of computations.
An image to be output after computer-aided image processing is normally a clear image with its all objects in focus without blurring, and may be more realistic if it is blurred depending on the type, movement, position, etc. of each object. To provide depth perception, for example, making an object near the focus clear and blurring an object out of focus in accordance with the depth of field are more preferable to making a closer object larger and a distant object smaller by simple perspective transformation. Further, it is preferable that an object which is moving fast should have some blur to the afterimage of the rear portion of the object, which is called motion blur. It is more realistic that a light source which has an extremely high luminance or an object on which light from such a light source is irradiated has blur around itself. Further, blur on an image opposite to semitransparent glass can present better expression of semitransparency. In some cases, it may be effective to always put blur on a specific object or polygon from the viewpoint of the progression of a game.
As apparent from the above, performing a blur process on a polygon makes an image to be displayed more realistic or more effective.
Conventionally, for example, the blur process spatially overlaps plural pieces of image data one on another, slightly shifting them. Alternatively, plural pieces of image data, shifted from one another over time, are overlapped one on another. Preparing plural pieces of image data however needs a very long image processing time, which results in an insufficient processing time to the preparation of the image data while reproducing ordinary motion on the display screen.